This is a Mason Wasp, Monobia quadridens. According to BugGuide it: “Usually nests in wood borings, but sometimes burrows in dirt banks. Sometimes takes over abandoned nests of carpenter bees or ground bees, also Sceliphron (mud dauber) cells. Nest is provisioned with caterpillars, and cells of nest are separated by mud partitions.” We do not believe this Mason Wasp is damaging your deck, and you do not neet to fear that it will “eat” it to the point that it is structurally compromised. The advantage of the caterpillars from your garden that will be used to feed its young far outweighs any damage done to the deck.